In such a system the drives of a respective floor-treatment device are controlled as a function of obstacle information about obstacles detected by the respective floor-treatment device, with obstacles being constituted by at least real objects, such as for example walls whose obstacle information is detected by sensors on the respective floor-treatment device while a respective floor-treatment device recording environment images in temporal and/or spatial intervals at points along the travel path by a camera that is carried along.
A plurality of floor-treatment devices that work in a temporally parallel manner can thus form a group of floor-treatment devices.
Moreover, the invention also relates to a floor- or ground-treatment device for carrying out the method.
Self-driving floor- or ground-treatment devices are known in the prior art in a multitude of designs. Typical representatives of such floor-treatment devices are robotic vacuum cleaners, robotic floor scrubbers, or robotic lawnmowers. The invention can relate to any type of such devices and preferably to robotic vacuum cleaners.
The floor-treatment devices each have controlled, particularly feedback-assisted drives, so that these floor-treatment devices are able to move automatically over the floor surface. These drives typically comprise two independently controllable wheels and a freely rotatable swivel caster or ball, with cornering being performed by controlling the wheels at different rotational speeds, particularly so that so-called differential steering is achieved. Control is effected by electronics integrated into the device and take over the navigation of the device on a floor surface, for example as a function of sensor signals or calculated values.
Typical floor-treatment devices can have a device body with a circular footprint, for example, with a floor-treatment device being integrated into the device body on the bottom side, particularly between the wheels, such as in a vacuum-cleaning device or a rotating blade, for example.
The driven wheels can have wheel sensors in order to provide travel-distance data for the navigation of such a device, such as specifically traveled routes.
The devices, which preferably move on only one plane, have sensors that are suitable for detecting obstacles in the context of navigation, for example collision sensors that respond to touch, or preferably noncontact sensors formed for example as laser scanners.
It is known in this context to use a laser that rotates on a horizontal plane in order to detect distances to obstacles in an angle-dependent manner, or also a fixed number of laser beams, all of which emanate from the device on a preferably common horizontal plane in order to sense, with each one of these beams, several distance values to a respective obstacle or even to several obstacles at then-established angles relative to the direction of motion of the device.
On the basis of obstacle information that is detected in this way and thus preferably consists of several value pairs of angles and distance, a floor-treatment device can preferably navigate in a collision-free manner, particularly to carry out a first type of navigation.
It is known in the prior art to implement a navigation algorithm in the controlling electronics of such a device with which so-called wall tracking can be performed on a real wall of a room, for example, or another real obstacle can be tracked, which preferably means that the device travels parallel to an extension of the obstacle, such as a wall at a controlled spacing. It is also known for such a device to move freely in the space on a straight path, for example, until it comes across an obstacle and turns around.
In the prior art, the type of trajectory traveled is specified beforehand in the electronics, usually as a meandering path or spiral path. In case of a predefined meandering path, this means that a floor-treatment device reverses its direction of motion when an obstacle has been detected in front of it and travels back at a spacing from its own previously traveled path. It is irrelevant whether the previously traveled path ran along a wall or was in open space.
In such a navigation algorithm for driving along one or more obstacles, which is inherently sufficiently known in the prior art and to a person skilled in the art, value pairs of angle (at which the device “sees” the obstacle) and distance (at this angle), for example from the midpoint of the device to the obstacle, are delivered to the algorithm, upon which the algorithm calculates a distance value to the obstacle transverse, preferably perpendicular to the direction of motion, provided that it is not also provided by the sensor(s), and maintains the spacing from a target value by controlling the drives of the wheels.
It is also known in the prior art to perform navigation by so-called local visual homing. Local visual homing is a term for a group of methods in which a vector, the so-called home vector, is calculated from two images that were recorded at different locations and indicates the direction from the location at which one of the images was recorded to the location at which the other image was recorded. The spacing between the two locations is not calculated.
If several, for example a plurality of images is available, triangulation can be employed on at least two home vectors using known spacings between the locations in order to determine the spacing from the device to a path along which the floor-treatment device has already traveled and along which it has recorded several images itself.
The possibility thus exists to even navigate on the basis of environment images that were recorded at locations at which a treatment device has already been. Different ways of carrying out local visual homing are known in the prior art and also sufficiently familiar to a person skilled in the art.
For example, DE 10 2007 016 802 describes how a floor-treatment device performs distance control to its own previous path on the basis of environment images that were recorded on its own predefined meandering or spiral travel path and the method of local visual homing through triangulation based on calculated home vectors.
Since the homing method is performed using environment images that were recorded by the device itself and the device travels along a predefined, in this case meandering path, the device knows which of the environment images it must use in each case for triangulation and distance control on its new path segment; after all, in the case of a reversal of direction, the device travels in the reverse sequence past the locations at which it recorded environment images on the previous path. The selection of the images to be used is performed here on the basis of absolute metric information by means of which the required images are accessed.
In the prior art, the (for example meandering) path is specified by determining a point on the path to be traveled to which the floor-treatment device is to travel from its current location, and the floor-treatment device is controlled appropriately in order to reach that point. In order to establish the point, the type of path to be traveled must have been stored in the electronics of the device. Each point to be traveled to must satisfy the criterion of lying on the predefined path. A path is thus composed of a plurality of specified points that are traveled to one after the other.
It is thus possible, for example, to perform (for example meandering) navigation on parallel predefined paths, starting from a path parallel to a wall obstacle, for example, even if the original wall obstacle can no longer be “seen” by the distance sensors because it is too far away, or even starting from a path that passes freely through space.
For this reason, sensor-based navigation on the basis of obstacle information (angle, distance) and local visual homing is often combined in floor-treatment devices. In the prior art, however, navigation around obstacles momentarily suspends the otherwise prevailing path specification.
Both in the invention that will be described herein and in the prior art, environment images are preferably employed for the purpose of navigating through local visual homing represent a 360° panorama of the surroundings of the location at which the environment image is recorded. To this end, the vertical optical axis of a camera can be pointed at the midpoint of a hyperbolic mirror, for example, so that a horizontal 360° panoramic image is recorded.
In the prior art, particularly in the art cited above, it is regarded as disadvantageous that homing-based navigation can only be carried out if the floor-treatment devices have acceptable computing capacity, if the path to be navigated, as described above, is known beforehand, and if it follows from that knowledge which environment images of previous path points are to be used for the local visual homing that is to be carried out. It is therefore not possible for any desired path shape to be covered in the prior art.
The known procedure of this prior art also assumes that the floor-treatment device travels past its own previously traveled path, since otherwise no environment images can be identified on the basis of which homing can be performed.
If several floor-treatment devices are optionally used on the same floor surface, multiple treatments of the same areas of the surface by different floor-treatment devices would therefore occur, which entails redundant effort.